Cellular localization and enzyme activity of alkaline phosphatase and several lysosomal enzymes are being studied by light and electron microscopy. These enzymes are localized within odontoblast and ameloblast cell populations and are related to the degree of mineralization found in the forming dentin-enamel junction. Scanning electron microscopy and x-ray microanalysis are also used to describe the accumulation of calcium, phosphorus, magnesium, and other ions at the mineralizing sites in the developing tooth. BIBLIOGRAPHIC REFERENCE: E. Burger, J.L. Matthews, S.B. Doty: Cellular calcium distribution in fetal bone and cartilage as studied by K-pyroantimonate and x-ray micro-analysis. In: The Sixth Parathyroid Conference, Vancouver, British Columbia. 1977 (in press).